Hiya, I feel so sorry for you. it's horrible having that niggling pain going on for what seems like forever.
I had it in my early 20s.. also had a second growth spurt! I went from having a decent size chest to comedy boobs - they're not that bad really :p but the discomfort did go away.
I too wear t-shirt bras (mostly) they seem to feel a little softer around the breast area. But now matter how much I pay for them or how well fitted they are, the shoulder dips are there - which ache from time to time.
I really hope you find an answer soon and definitely get checked in terms of fitting.